As an added bonus to the package you also get "day one access to the highly versatile DAO-12 semi-automatic shotgun itself," reads the EA press release, not just the fancy ammo. Only GAME and Gamestation in the UK have this offer available. Official blurb:

"Players can storm the battlefield armed with powerful weapons and items only available in the Physical Warfare Pack including the Type 88 light machine gun with bipod for superior firepower and total zone control, the SKS sniper rifle flash suppressor that provides increased stealth abilities for Recon soldiers, and the lethal armor-piercing flechette ammo for the DAO-12 semi-automatic shotgun that is sure to tear through anything in its path. Also included is day one access to the highly versatile DAO-12 semi-automatic shotgun itself."

Beside those weapons you also get the 'Back to Karkand' expansion to the game which lets you "wage all-out war on four of the most celebrated maps from Battlefield 2," which include the Strike at Karkand, Gulf of Oman and the Sharqi Peninsula.